1. Technical Field
This disclosure relates to circuit breakers, and more particularly, to a device and method for improving performance of a main contact in a short circuit condition.
2. Description of the Related Art
A circuit breaker is an important part of an electrical power system. The breaker ensures maximum current limiting without increasing damage to the breaker itself. Loss of union between contacts and blades of a breaker is a common problem when an arc occurs. This can occur due to heat and/or high current through the breaker. Heat and high current may result in damage to the breaker.
In one instance, heat is caused due to the bad placement of a weldment between the blade and the contact. This problem may be caused by the lack of filler metal at the surface where the contact is welded. When brazing or soldering, flux can be eliminated by using a phosphorus bearing filler metal, e.g., Sil-Fos® or solder. This filler metal typically flows during the joining process.
Referring to FIG. 1, two blades 12 and 14 are separately fabricated. The blades 12 and 14 are joined by a weld 22 formed using a welding process 20, e.g., an ultrasonic welding process. After welding, features such as a protrusion 16 and a corresponding locating hole 18 are aligned. Protrusion 16 and locating hole 18 provide a feature that is used to attach an operating spring.
Referring to FIG. 2, the two blades 12 and 14 are simultaneously joined to a contact 22 by soldering or brazing. The blades 12 and 14 include a gap 26 between them. Solder or filler metals 24 wick into the gap 26 and rob the joint between contact 22 and blades 12 and 14 of the filler metal. This prevents a good union between the blades 12 and 14 and the surface contact 22. Since the joint between the contact 22 and the blades 12 and 14 is very active during the operation of a circuit breaker, a poor joint here results in poor performance of the circuit breaker. Resistive heat can be generated and even arcing may occur in particularly bad joints.